Comparing wafer-scale and meter-scale atomic layer deposition of aluminum fluoride as an alternative aluminum-based mirror protective coating focusing on a high responsiveness in the far ultraviolet

Traditional atomic layer deposition (ALD) systems, designed for small ~200 mm substrates, limit ALD's application in astronomical instrumentation. Our previous work introduced a meter-scale ALD (MSALD) system, accommodating larger ~900 mm substrates. Utilizing the MSALD system, we prepared aluminum oxide (AlOx) to protect silver-based telescope mirrors, demonstrating scalable ALD processes with optimized parameters. This opened avenues for diverse materials like aluminum in telescope mirror applications. Our current investigation explores the MSALD systems’ potential to create aluminum fluoride (AlFx) protection coatings for aluminum-based telescope mirrors operated in the far UV spectral range. Unlike traditional AlOx, ALD of AlFx is uncommon, posing new challenges for achieving a uniform 2 nm coating due to the oxidation of Al surfaces. Our study, along with MSALD system modifications, yields crucial insights into scaling ALD for AlFx coatings, offering unique solutions to enhance Al-mirrors' performance and durability.